From: CCIE KH49279 (ccie_lab@inetiq.com)
Date: Wed Feb 22 2006 - 13:25:44 GMT-3
Jens,
Since we do not know what exactly your topology looks like we can still take
a nice theoretical discussion about this. Upfront I highly recommend running
some kind of dynamic IGP when using BGP.
When introducing people to BGP and such I like to explain to them that BGP
is reachability protocol which relies on your routing table (built either
statically or dynamically) for directions. With this being said, you gain
the most from your BGP/IGP combination than you will from BGP/Static. If I
rely on static routes for these directions, then I am limiting my scope and
capability to provide directions.
In the event you pursue selling/using l2/l3 VPN's you will want to use some
dynamic IGP to help build these tables as well. I suspect as an ISP you will
eventually, if not already, have the requirements to supply BGP and MPLS
based VPN's. Go to http://www.netcraftsmen.net/welcher/papers/mplsvpn.html
for some info on that.
Also consider the use of a dynamic "IGP as the glue that binds all the
routers in your AS together". You will find that using an IGP (even rip) can
provide a level of scalability that cannot be reached with static routes.
(to all the "nay" sayers out there, I am not advocating 100% non-use of
static routes, merely limited use).
A simple OSPF or EIGRP configuration is more easily managed in an ops
environment than hundreds of static routes. If your ops guys need to wrap
their heads around each routers static routes, they are then performing the
function of the IGP, albeit much less effective and efficient.
In a small enough network you can probably configure enough static routes to
cover yourself in the event of multiple failures, but most likely you can
find scenarios where static routes will give you less than efficient
routing, and in some cases big gapping black holes. While using OSPF or
EIGRP will allow for "efficient routing" beyond the scope of statically
configuring next hops, you will dynamically find the best path which you can
tune by the way, so if there are preferences that say an IGP is not
selecting, you can tweak to make it happen.
I suggest doing some reading of the benefits of ospf and eigrp. Then make
your case around how each protocol benefits and impacts both your operations
and design. If you deal with a vendor like Cisco or one of their partners,
they will be able to provide an array of case study material where an IGP
was ultimately selected over static routes, and detail more business case
information that you will be able to draw from.
Wayne
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Jens
Petter Eikeland
Sent: Wednesday, February 22, 2006 5:11 AM
To: ccielab@groupstudy.com
Subject: bgp/ospf
Can anybody try give me some good arguments for running bgp over ospf
internaly compared to running bgp over static routes.. We are going soon to
design redundancy in to our net and I am trying to tell that this would work
best with running dynamic routing in under BGP. There is a guy that are
trying to convince me that running only BGP would be better (with static
routes). We have this today. I am trying to say that this is not a good
solution. We have over 200 static routes on our core router, and it is not
very easy to keep track of anything... Anyway, when we are going over to
both have internal redundancy (internally)and external redundancy to our ISP
how could this possible be scalable with static routing. We are an ISP, and
have got many tousen customers that we are going to get in to to net soon.
This will generate more static routes... My suggestion is that we run OSPF
internally with BGP on every router in out core net, but he is saying that
keeping static routes and BGP is still the best solution..
Looking for some good arguments
Jens
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